The phrase "one's new year" refers to a person's first day or moment of starting something anew. It could be interpreted as the beginning of a fresh start, a clean slate, or a new chapter in one's life. This phrase is often used when someone has made a significant change or decision that marks a turning point for them. For example, if someone decides to quit their job and pursue a new career path, they might say "today is my new year." It implies that from this moment onwards, everything changes - it's the start of something different, exciting, and full of potential.